U.S. Pat. No. 4,534,743 issued Aug. 13, 1985, to Anthony D'Onofrio and Walter Kitik describes a process for making flexible split-electrode electroluminscent lamps by applying required lamp component layers in succession on a carrier strip which itself becomes part of the lamp. The disclosed process involves depositing a slurry of uncured epoxy resin and electroluminescent phosphor particles on a transparent conductive coating (indium-tin oxide) previously applied to a transparent flexible insulating carrier strip (Mylar.RTM. strip) The slurry coated strip is passed through a curing oven to cure the epoxy resin to bond the phosphor particulate in a flexible matrix and to adhere it to the coated carrier strip. Then, a slurry of liquid-borne conductive particulate is continuously deposited on the cured strip and the slurry dried to provide a second continuous coating of electrically conductive material; e.g., a nickel-filled acrylic coating. The laminated panel is then subjected to the split-electrode forming steps described in the patent.
U.S. Pat. No. 4,449,075 issued May 15, 1984 to Anthony D'Onofrio and Jack Gunzy, and U.S. Pat. No. 4,532,395 issued July 30, 1985 to Raymond Zukowski, involve an electroluminescent lamp driver circuit and an electroluminescent flexible touch switch panel, respectively.
Other prior art workers have used a slightly different process to manufacture individual electroluminescent lamps one at a time on a non-continuous basis (i.e., not using a continuously moving carrier strip), wherein the slurry of binder resin or material and electroluminescent phosphor particles is deposited on a piece of aluminum foil which functions in the lamp as the back or rear electrode. A transparent front electrode is placed over the dried phosphor layer on the back electrode and front leads and buss bar are attached to it to form the electroluminescent lamp. A dielectric layer is applied to the transparent front electrode on the side facing the deposited phosphor layer.
The slurry deposition process for depositing the phosphor particles suffers from disadvantages such as difficulty in obtaining uniform coverage of the substrate by the phosphor and stacking of phosphor particles atop one another. Non-uniform phosphor coverage results in voids in the phosphor layer. Increased voltage in driving lamps is required when voids are present in the layer. Stacking of phosphor particles in the layer increases the layer thickness. The buried phosphor particles absorb voltage without contributing to light output and also result in the lamp requiring more driving voltage. In general, the slurry process is difficult to control.
U.S. Pat. No. 2,728,870 describes a process for increasing light output of an electroluminescent lamp by heating the cured resin/phosphor layer after deposition on a substrate to the melting temperature of the resin while subjecting the heated layer to a D.C. electric field to impart a common alignment to the phosphor particles after cooling of the layer.
Technical article entitled "High Brightness Electroluminescent Lamps of Improved Maintenance" published by R. J. Blazek in Illuminating Engineering, November, 1962, provides information on construction of electroluminescent lamps and factors affecting their brightness or light output.
Similarly, a technical article entitled "Lasers, EL, and Light Values" published in Display Systems Engineering, pp. 379-391, 1968, discusses factors which affect performance of electroluminescent lamps.